1. Field of the Invention
The present invention relates to a polyetherketone (PEK) and a heat-resistant blend of polyvinylchloride (PVC) with the same, and more particularly, to a dendritic or hyperbranched PEK which exhibits miscibility with PVC and allows for melt blending with PVC, and a heat-resistant blend of PVC with the PEK.
2. Description of the Related Art
PVC, the most common type of polymer in use, has a broad range of applications, for example, pipes, soft films for packing food, fibers, interior articles, and the like. However, PVC has a low glass transition temperature (Tg) and a low heat distortion temperature (HDT), which restricts the applications of PVC at a high-temperature range. For example, a commercial PVC exhibits a glass transition temperature of about 85xc2x0 C. Thus, it would be highly desirable and commercially advantageous to improve the heat-resistance of PVC and thereby provide the PVC with higher temperature end-use applications, such as hot water pipes.
To meet this need, research into a technique for manufacturing linear polymers which exhibit a high degree of miscibility with PVC and offer high glass transition temperatures and blends of PVC with the same has been conducted. Most of linear polymers synthesized to satisfy this need further have polar groups at the backbone of common linear polymers.
For example, U.S. Pat. No. 4,698,390 teaches heat-resistant blends of PVC containing a linear polycarbonate, the glass transition temperature of which has been increased by adding sulfonic groups to the backbone of the polycarbonate. However, the problem with this PVC blend lies in the use of a solution blending method which cannot be applicable to mass production systems for commercial purpose. As another example, heat-resistant blend of PVC with polar linear polyarylates has been suggested by S. -Y. Kwak et al., in an article entitled xe2x80x9cEffect of Molecular Structure of Polyarylates on the Compatibility in Polyarylate/PVC blends, Journal of Applied Polymer Science, 70, 2173, 1998. However, in this disclosure a solution blending method has been adopted rather than the melt blending method which is commercially practicable for the heat-resistant blends of PVC.
The difficultly in applying the melt blending method to prepare PVC blends is based on the following. First, PVC has a specific hierarchy structure and includes microcrystallites which serve to provide for physical crosslinks within the structure, so that its temperature range of melt processing is restricted, for example, to a temperature of 180 to 210xc2x0 C. Second, for high temperature end-use applications of PVC, for example, for use of PVC in making hot water pipes, it is required to blend PVC with linear polymers having glass transition temperatures greater than or equal to 160xc2x0 C. In addition, when the melt blending technique is applied to blend PVC with a linear polymer having such a high glass transition temperature, melt blending temperatures should be 70 to 100xc2x0 C. higher than the glass transition temperature of the linear polymer added, i.e., in the range of 230 to 260xc2x0 C. to allow for easy melt blending. The reason is because the linear polymer has much entanglements in the melt state. As a result, PVC which exhibits weak thermal stability deteriorates at the high temperature.
In view of the above, it is an object of the present invention to provide a hyperbranched polyetherketone (PEK) which has a glass transition temperature (Tg) above 160xc2x0 C. and offers a high degree of miscibility with polyvinylchloride by melt blending at a relatively low temperature of 180 to 210xc2x0 C. within a short period of time.
It is another object of the present invention to provide a heat-resistant PVC blend with the hyperbranched PEK, which is applicable to high temperature end-use products such as hot water pipes.
The first object of the present invention is achieved by a PEK synthesized by self-polycondensation of 3,5-bis[4-[(2,3,4,5,6-pentafluorophenyl)carbonyl]phenoxy]-4-hydroxybenzophenone having the formula (1) 
Another embodiment of the PEK according to the present invention is synthesized by fluorine substitution reaction from PEK polymerized from 3,5-difluoro-4xe2x80x2-hydroxybenzophenone having the formula (2) 
Preferably, 50 to 80 mole % of fluorine atoms present in the molecular structure of the PEK polymerized from 3,5-difluoro-4xe2x80x2-hydroxybenzophenone having the formula (2) hereinabove are substituted by polar groups having the formula (3)
xe2x80x94Oxe2x80x94Axe2x80x94CNxe2x80x83xe2x80x83(3)
wherein A represents 
or alkylene groups of 1 to 3 carbon atoms, n has a value of from 0 to 2, and m has a value of 0 or 1, which allows for easy melt blending with PVC within a short period of time at relatively low temperatures.
Preferably, in the formula (3) A is 
xe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CH2CH2CH2xe2x80x94, xe2x80x94CH(CH3)xe2x80x94 or xe2x80x94C(CH3)2xe2x80x94.
Preferably, the degree of branching of the PEK synthesized from the monomer of formula (1) is in the range of 0.4 to 0.6.
The second object of the present invention is achieved by a blend of PVC comprising: one of the previously mentioned PEKs in a ratio of 10 to 50 percent by weight of the total blend; and PVC in a ratio of 90 to 50 percent by weight of the total blend.
Preferably, the blend of PVC is manufactured by melt blending. Also, the melt blending may be carried out at a temperature of 180 to 210xc2x0 C. The blend of polyvinylchloride has a single glass transition temperature of 105xc2x0 C. or more in the differential power curve obtained by differential scanning calorimetry.
The hyperbranched PEK according to the present invention has a high glass transition temperature greater than or equal to 160xc2x0 C., and can be uniformly blended with PVC by melt blending at relatively low temperatures within a short period of time. Also, the hyperbranched PEK ensures that melt blending thereof with PVC is practicable for industrial use and does not cause deterioration of PVC, and thus the PVC blend with the PEK can be efficiently used in manufacturing high temperature end-use applications such as hot water pipes.